a a x1 b x1 a b x1 c c x1 b c x1 b a a x1 2.2 b c x1 a a x1 b c x1 a x1 b c x1 b a a x1 a a x1 b x1 true a a x1 b x1 b c x1 b a a x1 b c x1 a x1 b c x1 a a x1 true Failed! NaTT certifiable-1.6